Process for isolation of dicarboxylic acids and hydroxycarboxylic acids

ABSTRACT

A first process involves the partial electrodialysis of a dialkali metal salt of an aromatic hydroxycarboxylic acid or a dicarboxylic acid to produce the approximate monoalkali metal salt and the alkali metal hydroxide. The monoalkali metal salt is then treated with an acid such as a bisulfate to recover the aromatic hydroxycarboxylic acid or dicarboxylic acid. The resulting inorganic salt such as sodium sulfate may then be electrolyzed to sodium bisulfate and NaOH. A second process involves the electrodialysis at elevated temperatures of a (di)alkali metal salt of p-hydroxybenzoic acid produce free p-hydroxybenzoic acid and the alkali metal hydroxide. These are efficient and economical methods for recovering the acid and alkali metal hydroxide values, as well as the parent organic compound, from these dialkali metal salts.

This application claims the priority benefit of U.S. ProvisionalApplication 60/014,998, filed Apr. 8, 1996.

FIELD OF THE INVENTION

This invention concerns a process for the isolation of dicarboxylicacids and aromatic hydroxycarboxylic acids from their alkali metal saltsby partially electrodialyzing these salts and then reacting the salt ofthe dicarboxylic acid or hydroxycarboxylic acid with a Bronsted acid.This invention also concerns a process for the isolation ofp-hydroxybenzoic acid from its mono- or dialkali metal salts byelectrodialyzing these salts. Alkali metals and their hydroxides may becompletely and economically recycled in the process.

BACKGROUND OF THE INVENTION

Aromatic hydroxycarboxylic acids and dicarboxylic acids are importantitems of commerce. For instance o-hydroxybenzoic acid (salicylic acid)is used as a chemical intermediate, for instance to make aspirin, whilep-hydroxybenzoic acid (PHBA) is used to make parabens and is also usedas a monomer in making polyesters, while dicarboxylic acids areimportant as monomers. Traditionally aromatic hydroxycarboxylic acidsare manufactured using the Kolbe-Schmitt reaction, which is a reactionof an alkali metal salt of an aromatic hydroxy compound with carbondioxide, usually under elevated temperature and pressure.

The Kolbe-Schmitt reaction has been a standard procedure for thepreparation of aromatic hydroxy acids for over 100 years, see forinstance A. S. Lindsey, et al., Chem. Rev., vol. 57, p. 583-620 (1957)incorporated by reference herein. However, this process is complex anddifficult to run, involving several manufacturing steps, which adds tothe cost of the final product. Since the initial product of thecarboxylation reaction is a dialkali metal salt of the aromatichydroxycarboxylic acid, substantial cost is usually incurred for the useof compounds such as NaOH or KOH which are subsequently discarded (assodium or potassium salts), since the free aromatic hydroxycarboxylicacid (or dicarboxylic acid) is usually isolated by reacting the dialkalimetal salt with a strong acid. It is hence desirable to develop animproved Kolbe-Schmitt process for the manufacture of these compounds.Dicarboxylic acids are also sometimes available as their dialkali metalsalts, and it is often desirable to convert these to the dicarboxylicacids themselves, and generate an alkali from the alkali metals presentin the salts.

It is known that the salts of diacids or aromatic hydroxycarboxylicacids can be electrodialyzed to form the free dicarboxylic acid oraromatic hydroxycarboxylic acid and the alkali metal hydroxide. However,when one tries to completely electrodialyze these compounds to thesefinal products, as one approaches complete electrolysis, the voltageincreases and the current efficiency decreases rapidly and the processmay become uneconomic. Therefore, it would be desirable to have anothereconomical method for isolating the free aromatic hydroxycarboxylic acidor dicarboxylic acid from its dialkali metal salt, while at the sametime being able to recycle the alkali metals in the process in aneconomical fashion.

Japanese Patent Application 40-11492 describes the electrodialysis of analkali metal salt of terephthalic acid to terephthalic acid and analkali metal hydroxide.

Japanese Patent Application 64-9954 describes the electrodialysis of analkali metal salt of hydroxybenzoic acid.

None of the above references describes a partial electrodialysisfollowed by a treatment with a strong acid to effect isolation of adicarboxylic acid or an aromatic hydroxycarboxylic acid.

Electrodialysis of salts of organic compounds is in general known, andgenerally requires only relatively simple equipment. However, if oneattempts to electrodialyze an aqueous solution of the mono- ordipotassium salt of PHBA, one finds that before free PHBA is obtained,the voltage required to effect electrolysis greatly increases and theelectrolysis essentially stops (see Comparative Example 1). However ithas now been found that if this electrodialysis is done at elevatedtemperatures, good results can be obtained.

SUMMARY OF THE INVENTION

A first process of this invention for the preparation of a dicarboxylicacid or an aromatic hydroxycarboxylic acid from its dialkali metal salt,comprises,

(a) electrodialyzing a compound of the formula (OR¹ CO₂)M₂ or R² (CO₂)₂!M₂ to produce a compound of the formula (OR¹ CO₂)H_(y) M_(2-y) or R²(CO₂ )₂ !H_(y) M_(2-y) and MOH; and

(b) reacting (OR¹ CO₂)H_(y) M_(2-y) or R² (CO₂)₂ !H_(y) M_(2-y) with:

a Bronsted acid of the formula M_(q) H_(s-q) X whose pKa in water isabout 4 or less; or

an aqueous solution of a Bronsted acid of the formula HT whose pKa inwater is about 4 or less, said aqueous solution optionally containing atleast 5 mole percent of HT or MT;

to form (OR₁ CO₂)H₂ or R² (CO₂)₂ !H₂ and a T or X salt of M, andwherein:

T is monovalent anion;

R¹ is arylene or substituted arylene

R² is hydrocarbylene or substituted hydrocarbylene;

M is an alkali metal cation;

s is the valence of X;

y is about 0.10 to about 1.90;

q is about 0.10 to about (s-0.10); and

X is a polyvalent anion.

A second process of this invention for the preparation ofp-hydroxybenzoic acid from its dialkali metal salt, comprises,electrodialyzing an aqueous solution of a first compound of the formula(OR¹ CO₂)H_(y) M_(2-t) to produce a second compound of the formula (OR¹CO₂)HyM₂ -y and MOH, wherein:

R¹ is p-phenylene;

t is zero to about 1.50;

M is an alkali metal cation; and

y is about 1.95 to 2.00;

and provided that when y or t is about 1.0 or more, said electrodialysisis carried out at a temperature of about 75° C. or more.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a graph showing data from Example 1 of electrolysis time vs.pH of the solution in the central compartment of the electrodialysiscell.

FIG. 2 is a graph showing data from Comparative Example 1 ofelectrolysis time vs. pH of the solution in the central compartment ofthe electrodialysis cell.

DETAILED DESCRIPTION OF THE INVENTION

The product of the first process of the invention is an aromatichydroxycarboxylic acid or a dicarboxylic acid or a partial alkali metalsalt thereof.

By an aromatic hydroxycarboxylic acid is meant a compound that containsat least one aromatic carbocyclic ring, and at least one hydroxyl groupand one carboxyl group, both of which are attached to a carbon atom ofan aromatic carbocyclic ring. This compound may contain one or morearomatic rings, and if more than one such ring is present they may befused, as in naphthalene, connected by a covalent bond, as in biphenyl,or by a divalent group, as in diphenyl ether. There may also be inertgroups attached to the aromatic ring(s), such as one or more alkylgroups. Compounds which may produced by this process includep-hydroxybenzoic acid, o-hydroxybenzoic acid, 2-hydroxy-3-methylbenzoicacid, 2-hydroxy-5-methylbenzoic acid, 2,4-dihydroxybenzoic acid, and ahydroxynapthoic acid. Preferred products are p-hydroxybenzoic acid,6-hydroxy-2-napthoic acid, and o-hydroxybenzoic acid.

The product of the first process may also be a dicarboxylic acid. It ispreferred that the product is an aromatic dicarboxylic acid. By anaromatic dicarboxylic acid is meant a compound that contains at leastone aromatic carbocyclic ring, and also contains two carboxyl groupsattached to carbon atoms of one or more aromatic carbocyclic ring. Thiscompound may contain one or more aromatic rings, and if more than onesuch ring is present they may be fused, as in naphthalene, connected bya covalent bond, as in biphenyl, or by a divalent group, as in diphenylether or diphenylmethane. There may also be inert groups attached to thearomatic ring(s), such as one or more alkyl groups and/or halogens.Preferred product aromatic dicarboxylic acids are isophthalic acid,terephthalic acid, 4,4'-bibenzoic acid, and 2,6-naphthalene dicarboxylicacid.

By arylene herein is meant a radical with two free valencies to carbonatoms of one or two aromatic rings. By hydrocarbylene herein is meant adivalent radical containing carbon and hydrogen. By "substituted" hereinis meant one or more substitutents that don't interfere with thereactions described herein. Suitable substitutents include alkyl andhalogen.

The starting material for this first process is the correspondingdialkali metal salt of an aromatic hydroxycarboxylic acid ordicarboxylic acid or its partially acidified form of the formula (OR¹CO₂)H_(z) M_(2-z) or R² (CO₂)₂ !H_(z) M_(2-z), wherein z is less than 1,more preferably 0 to about 0.5 and especially preferably less than about0.1. This compound is then electrolyzed so that the value of z isincreased to y, y normally being greater than z. Usually there will beessentially only one alkali metal present, and sodium and potassium arepreferred alkali metals, and potassium is especially preferred. Thesedialkali metal salts may originate from any of several sources. Forinstance, the initial product of the Kolbe-Schmitt synthesis of aromatichydroxycarboxylic acids is a dialkali metal salt. A product of theHenschel synthesis of dicarboxylic acids is a dialkali metal salt. Bothof these processes start with alkali metal hydroxides. Using the firstprocess described herein, an essentially closed loop process withrespect to alkali metal may be envisioned.

For instance, in the Kolbe-Schmitt synthesis of salicylic acid, theprimary product is usually the disodium salt of salicylic acid. In theequations below, SA is salicylate dianion. These equations represent afirst process for the complete recovery of all alkali metal (sodium) andacid (in this case sodium bisulfate) values so they may be recycled inthe process.

    Na.sub.2 SA+electrodialysis→NaHSA+NaOH              (1)

    NaHSA+NaHSO.sub.4 →H.sub.2 SA+Na.sub.2 SO.sub.4     (2)

    Na.sub.2 SO.sub.4 +electrodialysis→NaHSO.sub.4 +NaOH(3)

In the above equations, M is Na, y is 1, R¹ i o-phenylene, y is 1, and qis 1.

Note that enough NaOH is produced in the process to be recycled back tothe beginning of the Kolbe-Schmitt process, and also enough NaHSO₄ isregenerated to continue the process. Note that equations (1) and (2)represent the essential steps of the process described herein, whileequation (3) represents an optional step which regenerates the neededalkali metal values for recycle in the overall Kolbe-Schmitt process. Afirst process for a monovalent anion would be as follows:

    Na.sub.2 SA+electrodialysis→NaHSA+NaOH              (4)

    NaHSA+HT+0.5NaT→H.sub.2 SA+1.5NaT                   (5)

    1.5NaT+electrodialysis→0.5NaT+NaOH                  (6)

Here the major difference is that unreacted NaT is simply carriedthrough equations (5) and (6). After electrodialysis the NaT and NaOHsolutions may be recombined for use in (5). Again the sodium may becompletely recycled in the overall Kolbe-Schmitt process.

Other preferred combinations of M and R¹ in the first process are M ispotassium and R¹ is p-phenylene, and M is potassium and R¹ is2,6-naphthylene.

The NaT or other non-reactive charge carrier which is carried throughthe processes of equations (5) and (6) need not be present in (5), butshould be in the process stream in (6), since if not done the currentefficiency in trying to convert all of the NaT in (6) to NaOH would bepoor.

Similar reactions in the first process may be envisioned for otheraromatic hydroxycarboxylic acids or dicarboxylic acids, other anions,and other alkali metals. Indeed, the anion may have any number ofnegative charges in similar schemes, just so long as the acid employedhas a pKa of about 4 or less.

In the first process Y may be about 0.10 to about 1.90, preferably about0.25 to about 1.75, is more preferably about 0.5 to about 1.5,especially preferably about 0.9 to about 1.4 and most preferablyabout 1. Q may be about 0.10 to about (s-0.10), preferably about 0.25 toabout (s-0.25), is especially preferably about 0.5 to about (s-0.50),more preferably about 0.75 to about (s-0.75) and when s is 2, especiallypreferably about 1.

Suitable acids for use in the first process that have a pKa of 4 or lessinclude HSO₄ ⁻, HCl, H₃ PO₄, F₃ CCO₂ H, and CF₃ SO₃ H. By a polyvalentanion is meant an anion that has more than one negative charge. It ispreferred that X is a divalent anion and hence s is 2. It is alsopreferred that X is SO₄ ⁼ (sulfate) anion, and it is preferred that T ischloride anion.

Electrodialysis is a well known process, see for instance B. Elvers., etal., Ed., Ullmann's Encyclopedia of Industrial Chemistry, 5th Ed., Vol.A16, VCH Verlagsgesellschaft mbH, Weinheim, 1990, p. 209-213 and245-250, which is hereby included by reference, and electrodialysis ofmetal salts of inorganic acids such as K₂ SO₄ and NaCl are especiallywell known. In effect, in reaction 3, and in all such reactionsinvolving anion X, in the compound MqH_(s-q) X s is being increased atthe expense of q and MOH is also being formed. In reaction 6 the ratioof HT to MT is increasing (HT is being formed) and MOH is also beingformed. Thus it may be said the Bronsted acid component of the solutioncontaining X or T is being increased. It is believed that because alkalimetal hydroxide is generated in the electrolysis processes herein andorganic compounds are also present, fluorinated membranes, such asNafion® Perfluorinated Membranes (from E. I. du Pont de Nemours andCompany, Wilmington, DE U.S.A.) are particularly useful in theseprocesses.

As the artisan will understand, a three compartment cell may be utilizedin the first process which utilizes the dialkali metal salt of thearomatic hydroxycarboxylic acid or dicarboxylic acid. These startingmaterials are fed to the center compartment, while alkali metalhydroxide will be generated in the cathode compartment. In the anodiccompartment oxygen is generated, while in the center compartment thecompound (OR₁ CO₂)HyM_(2-y) or R² (CO₂)₂ !H_(y) M_(2-y) is generated.Fresh solution of the alkali metal salt may be added to the centercompartment, and solution of the center compartment removed, at such arate so that "average" solute in the solution is (OR₁ CO₂)HyM_(2-y) orR² (CO₂)₂ !HYM_(2-y), as defined herein.

In the first process, if any of the salts of aromatic hydroxycarboxylicacid or dicarboxylic acid present in the cell has a limited solubilityin water, it may be desirable to heat the cell to increase thesolubility in water. Limited solubility may be encountered especiallywhen y is greater than 1, since "free" (not being an alkali metal salt)aromatic dicarboxylic acid or aromatic hydroxy carboxylic acid will bepresent, and the free organic compound may have only very limitedsolubility in cool water. The pH of the solution in the centercompartment is an indication of what the present value of y is in thatcompartment (see Example 1).

When M is potassium and R¹ is p-phenylene it is preferred to carry outthe process at a temperature of about 80° C. to about 105° C.,especially when y is about 0.9 or more. More generally when y is about0.9 or more it is also preferred to carry out the process at atemperature of about 80° C. to about 105° C. If the solubility of thefree aromatic dicarboxylic acid or aromatic hydroxycarboxylic acid inwater is relatively low, even at elevated temperatures, one may not beable to electrolyze the solution much past the point where y is about 1.

In the first process, in the electrolysis of M₂ X or MT, a two or threecompartment cell may used, the solution of the alkali metal salt beingfed to the anodic cell, or in the case of a three compartment cell, thecenter cell. The solution in the anodic cell may be withdrawn at such arate that a solution of MqH_(2-q) X is withdrawn. A three compartmentcell is preferable if T is a readily oxidizable anion, such as chloride.Here the solution may be withdrawn from the center compartment of athree compartment cell so that a proper mixture of HT and MT isobtained. MOH is generated in the cathodic cell of each.

The product of the second process of the invention is p-hydroxybenzoicacid, containing up to 5 mole percent of the monopotassium salt(y=1.95).

Obtaining complete electrodialysis to "pure" p-hydroxybenzoic acid mayrequire an inordinate amount of electrical energy, so it may be moreeconomical to leave a small amount of the monopotassium salt in the PHBAand purify the free compound as by crystallization. The monopotassiumsalt left in solution may be recycled back to the electrodialysis forrecovery.

The starting material for the second process is the corresponding mono-or dialkali metal salt of PHBA of the formula (OR₁ CO₂)H_(t) M_(2-t)wherein t is zero to about 1.5, more preferably 0 to about 0.5,especially preferably less than about 0.1, and most preferably about0.0. This PHBA salt is then electrolyzed so that the value of t isincreased to y, y normally being greater than t. Usually there will beessentially only one alkali metal present, and potassium is preferred.Using the process described herein, an essentially closed loop processwith respect to alkali metal (usually potassium) may be envisioned.

In the final product of the second process it is preferred that y isabout 1.97 or more.

A three compartment cell may again be utilized in the second processwhich utilizes an alkali metal salt of PHBA. This starting material isfed to the center compartment, while alkali metal hydroxide will begenerated in the cathode compartment. In the anodic compartment oxygenis generated, while in the center compartment the compound (OR₁CO₂)HyM_(2-y) is made. Fresh solution of the PHBA alkali metal salt maybe added (continuously or intermittently) to the center compartment, andsolution of the center compartment removed (continuously orintermittently), at such a rate so that "average" solute in the solutionis (OR₁ CO₂)H_(y) M_(2-y), as defined herein.

In the second process when y is about 1 or more the electrodialysis iscarried out above about 75° C. Thus two cells can be used in series ifin the starting alkali metal salt of PHBA t is about 1.0 or less. Inthis instance the temperature in the first cell is not critical, but inthe second cell, wherein y is about 1 or more, the temperature is about75° C. or more. Temperatures above the atmospheric boiling point ofwater in the solution may be used by placing the cell under elevatedpressure, but the preferred upper temperature limit for this part of theelectrodialysis is the boiling point of the aqueous solution atatmospheric pressure. The preferred minimum temperature is about 80° C.,and it is more preferred that the minimum temperature is about 85° C.

In the second process the concentration of the alkali metal salt of PHBAin the aqueous solution that is electrodialyzed is not critical, but notso high that free PHBA will crystallize out in the three compartmentcell. However, it is preferred that the concentration is high enough sothat the solution will readily conduct electricity. It is also preferredthat the solution concentration be relatively high so that isolation ofthe free PHBA after electrolysis is simplified. Isolation may beaccomplished by cooling the solution and separating the crystallizedPHBA. The filtrate containing some dissolved PHBA may be recycled backinto the electrodialysis, i.e., "new" alkali metal salt may be dissolvedin the filtrate and the solution electrodialyzed. A preferredconcentration of alkali metal salt in solution is about 10 to about 35percent by weight, more preferably about 15 to about 30 percent byweight, of free PHBA based on the total weight of water and free PHBAequivalent in the solution.

EXAMPLE 1

The electrochemical cell used was an ElectroCell AB (S-184 00Akersberga, Sweden) "Electro MP Cell" . This is was configured as athree compartment cell using Nafion® N-417 (formerly commerciallyavailable from E. I. du Pont de Nemours and Company, Wilmington, DE,U.S.A.) membranes. This membrane was a perfluorosulfonic acid polymerwith an equivalent weight of 1100 reinforced with a wovenperfluoropolymer fabric. The nominal thickness of the membrane was about0.25 mm, and it had conditioned resistance of 3.5-4.0 ohms-cm². Currentsimilar offerings of Nafion® include Nafione N-450 and Nafion® NE-424.The effective area of each of the anode and cathode was 0.01 m². Theanode was a dimensionally stable (DSA) oxygen anode, and the cathode wasstainless steel.

The PHBA solution was placed in a 2 L resin kettle with a lid and clamp.

The kettle was heated on a hot plate and was equipped with a magneticstirrer, pH meter electrode, thermometer, and process inlet and outletlines. The outlet line also had a porous thermoplastic disc filter init. The PHBA solution was passed through a glass vacuum trap which waswrapped with electrical heater tape and acted as an auxiliary heater.The PHBA was circulated to the center compartment of the electrolysiscell.

The catholyte was 1.5 of 1N KOH solution which was pumped from a heatedreservoir to the cathode compartment and then returned to the reservoir.The temperature of the catholyet was kept close to the PHBA solutiontemperature. The anolyte was 50 mL of concentrated sulfuric acid dilutedin 900 mL of distilled water. It was circulated by a pump from areservoir through the anode compartment back to the reservoir. Theanolyte had no separate heater. A solution of the dipotassium salt ofp-hydroxybenzoic acid (PHBA) was made by dissolving 120 g of PHBA and114.6 g of KOH (pellets nominally containing 85 weight percent KOH, 15%water) in 400 mL of water. This was circulated in the center compartmentof the cell, and the solution in all three compartments were separatelycirculated and heated to 90° C. (during the electrolysis the catholytewas 88 ° C. and the center compartment solution was 83° C. at the start,and at 90°±1° C. within 25 min after the start of the electrolysis). Theelectrolysis was started and continued so that the voltage was varied tomaintain a constant current of 15 A (ampere). During the electrodialysiswater was added as necessary to replace evaporative losses.

The voltages required vs. the time elapsed for selected times during theelectrolysis are shown Table 1

                  TABLE 1    ______________________________________    Time (min)    Voltage (v)    ______________________________________     1            5.09     50           5.09    100           5.19    150           5.42    200           5.57    250           6.27    270           7.03    300           8.63    310           9.62    320           10.14    330           8.94    340           8.19    ______________________________________

FIG. 1 shows the correlation of the pH of the center compartmentsolution with electrolysis time. It is believed that the inflectionpoint at about 150; min represents the point at which z is approximately1.0, or the compound present in solution is approximately themonopotassium salt of PHBA. As the time of electrolysis approaches 300min it is believed that z is becoming quite small, so that at perhapsabout 320 min the solute in the center compartment is almost pure PHBA.

COMPARATIVE EXAMPLE 1

The apparatus used was similar to that in Example 1 except the PHBAsolution reservoir was an open Erlenmeyer flask on a hot plate, andthere was no filter or auxiliary heater in the PHBA solution lines.

A solution of the dipotassium salt of p-hydroxybenzoic acid (PHBA) wasmade by dissolving 120 g of PHBA and 114.6 g of KOH (pellets nominallycontaining 85 weight percent KOH, 15% water) in 400 mL of water. Thiswas placed in the center compartment of the cell, and the solution inall three compartments were separately circulated. The electrolysis wasstarted and continued so that the voltage was varied to maintain aconstant current of 15 A (ampere). During the electrodialysis water wasadded as necessary to replace evaporative losses.

The voltages required vs. the electrolysis time elapsed for selectedtimes during the electrolysis are shown Table 2.

                  TABLE 2    ______________________________________    Time   Voltage      Remarks    ______________________________________     3      5.65     70     5.82     78     5.83    120     6.43    125     7.05    130     8.03    135     9.96    140    10.7         Gas bubbles at anode    145    11.8    150    12.2    155    13.1    160    13.9    165    14.5         Heat off to center compartment    180    15.4         Crystals forming in PHBA solution    240    20.4         PHBA inlet line plugged    255    19.6         Crystals at PHBA solution surface    261      50.0+      PHBA inlet line plugged    ______________________________________

It is clear that before complete electrolysis of the potassium salt ofPHBA could be accomplished the cell required excessive voltage tooperate, and in fact plugged with crystals that had formed in the PHBA(and/or its potassium salt) solution.

FIG. 2 shows a the correlation of the pH of the centercompartmentsolution with electrolysis time. It is believed that thesolution with inflection point at about 150 min represents the point atwhich y is approximately 1.0, or the compound present in solution isapproximately the monopotassium salt of PHBA. As the time ofelectrolysis went over 250 min, it is believed that y was approaching2.0.

What is claimed is:
 1. A process for the preparation of a dicarboxylic acid or an aromatic hydroxycarboxylic acid from its dialkali metal salt, comprising,(a) electrodialyzing a compound of the formula (OR¹ CO₂)M₂ or R² (CO₂)₂ !M₂ to produce a compound of the formula (OR¹ CO₂)H_(y) M_(2-y) or R² (CO₂)₂ !H_(y) M_(2-y) and MOH; and (b) reacting (OR¹ CO₂)H_(y) M_(2-y) or R² (CO₂)₂ !H_(y) M_(2-y) with: a Bronsted acid of the formula M_(q) H_(s-q) X whose pKa in water is about 4 or less; oran aqueous solution of a Bronsted acid of the formula HT whose pKa in water is about 4 or less, said aqueous solution optionally containing at least 5 mole percent of HT or MT;to form (OR¹ CO₂)H₂ or R² (CO₂)₂ !H₂ and a T or X salt of M, and wherein:T is monovalent anion; R¹ is arylene or substituted arylene; R² is hydrocarbylene or substituted hydrocarbylene; M is an alkali metal cation; s is the valence of X; y is about 0.10 to about 1.90; q is about 0.10 to about (s-0.10); and X is a polyvalent anion.
 2. The process as recited in claim 1 wherein y is about 0.75 to about 1.75.
 3. The process as recited in claim 2 wherein q is about 0.25 to about (s-0.25).
 4. The process as recited in claim 1 or 3 wherein s is
 2. 5. The process as recited in claim 4 wherein M is sodium and R¹ is o-phenylene, M is potassium and R¹ is p-phenylene, or M is potassium and R¹ is 2,6-naphthylene.
 6. The process as recited in claim 4 wherein M is potassium and R¹ is p-phenylene.
 7. The process as recited in claim 1 or 3 wherein X is SO₄ ⁻².
 8. The process as recited in claim 7 wherein M is sodium and R¹ is o-phenylene, M is potassium and R¹ is p-phenylene, or M is potassium and R₁ is 2,6-naphthylene.
 9. The process as recited in claim 7 wherein M is potassium and R¹ is p-phenylene.
 10. The process as recited in claim 7 comprising the additional step of electrodialyzing said T or X salt of M formed in step (b) to increase a Bronsted acid component of a solution containing X or T and to form MOH.
 11. The process as recited in claim 1 wherein q is about 0.25 to about (s-0.25).
 12. The process as recited in claim 1 or 11 wherein y is about
 1. 13. The process as recited in claim 12 wherein X is SO₄ ⁻².
 14. The process as recited in claim 13 wherein M is sodium and R¹ is o-phenylene, M is potassium and R¹ is p-phenylene, or M is potassium and R¹ is 2,6-naphthylene.
 15. The process as recited in claim 14 comprising the additional step of electrodialyzing said T or X salt of M formed in step (b) to increase a Bronsted acid component of a solution containing X or T and to form MOH.
 16. The process as recited in claim 13 wherein M is potassium and R¹ is p-phenylene.
 17. The process as recited in claim 16 comprising the additional step of electrodialyzing said T or X salt of M formed in step (b) to increase a Bronsted acid component of a solution containing X or T and to form MOH.
 18. The process as recited in claim 12 wherein M is sodium and R¹ is o-phenylene, M is potassium and R¹ is p-phenylene, or M is potassium and R¹ is 2,6-naphthylene.
 19. The process as recited in claim 12 wherein M is potassium and R¹ is p-phenylene.
 20. The process as recited in claim 12 comprising the additional step of electrodialyzing said T or X salt of M formed in step (b) to increase a Bronsted acid component of a solution containing X or T and to form MOH.
 21. The process as recited in claim 1, 2, 11, or 3 wherein M is sodium and R¹ is o-phenylene, M is potassium and R¹ is p-phenylene, or M is potassium and R¹ is 2,6-naphthylene.
 22. The process as recited in claim 21 comprising the additional step of electrodialyzing said T or X salt of M formed in step (b) to increase a Bronsted acid component of a solution containing X or T and to form MOH.
 23. The process as recited in claim 1, 2, 11, or 3 wherein M is potassium and R¹ is p-phenylene.
 24. The process as recited in claim 23 comprising the additional step of electrodialyzing said T or X salt of M formed in step (b) to increase a Bronsted acid component of a solution containing X or T and to form MOH.
 25. The process as recited in claim 23 wherein said process is carried out at about 80° C. to about 105° C. when y is about 0.9 or more.
 26. The process as recited in claim 1, 2, 11 or 3 comprising the additional step of electrodialyzing said T or X salt of M formed in step (b) to increase a Bronsted acid component of a solution containing X or T and to form MOH. 